This invention relates to a multiple beam scanning radar system.
In a radar systems, such as a three dimensional radar systems, requiring accurate information on range, azimuth and altitude of a target, accuracy of azimuthal and altitude information depends greatly on antenna characteristics. Therefore, an antenna forming a pencil beam with an acute directional pattern is suitable for the above-mentioned radar. A radar system rotating the antenna at high speed to scan a space by the pencil beam has been employed extensively. However, the pencil beam scanning system requires a comparatively long time for scanning the space, which may cause a restriction to update rate (radar data rate) of a target information.
A multiple beam scanning system is then taken up as an effective means to settle the above-mentioned restriction. The scanning system forms multiple beams by radiating multiple high-frequency pulse signals of different frequencies simultaneously from an antenna, so as to increase the update rate of information effectively.
In a conventional radar employing this system, a transmitter consisting of an exciter for generating a high-frequency signal in a predetermined frequency and an amplifier for amplifying the high-frequency signal is prepared in the number equal to that of beams to be formed as above, and each amplifier output is supplied to a predetermined feed terminal of the antenna through a duplexing circulator. The high-frequency signal supplied to each feed terminal is predetermined, an the number of the feed terminals is equal to the number of beams to be formed. A plurality of corresponding beams are formed by the antenna according to the high-frequency signal of a plural frequency thus supplied. On the other hand, after passing each feed terminal of the antenna, the signal received on the antenna is separated from a transmitting side by the circulator and then led to a receiver, where only a frequency component of each transmitter system is extracted, amplified and then detected. A signal processor receives a plural frequency component thus obtained and performs normal radar signal processing necessary for target acquisition and display.
The above-described conventional multiple beam scanning radar system requires one transmitters for each beams to be formed, therefore not only does the configuration become complicated but also the system is very costly.